Identification—
A:
Place a small piece of it on a salt plate, add 1 drop of acetone, and promptly cover with another salt plate. Rub the plates together to dissolve the specimen, slide the plates apart, and allow the acetone to evaporate: the IR absorption spectrum of the film so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of
USP Docusate Potassium RS.
B:
It responds to the flame test for
Potassium 
191
.
Limit of bis(2-ethylhexyl) maleate—
Place 12.5 g of Docusate Potassium, previously dried and accurately weighed, in a 100-mL volumetric flask. Pipet 20 mL of pH 10 alkaline borate buffer (see under
Solutions in the section
Reagents,
Indicators,
and Solutions) into the flask, and add about 70 mL of alcohol. Swirl the flask and contents, with gentle warming if necessary, until the solid dissolves. Adjust the reaction dropwise, if necessary, with 1 N sodium hydroxide to a pH of 10. Add alcohol to volume, and proceed as directed in the test for
Bis(2-ethylhexyl)maleate under
Docusate Sodium, beginning with “Transfer a portion of this solution to a polarographic cell.” The diffusion current for the test solution of Docusate Potassium is not greater than one-half the diffusion current of the solution containing the added bis(2-ethylhexyl)maleate [not more than 0.4% of bis(2-ethylhexyl)maleate].
Assay—
Tetra-n-butylammonium iodide solution, and Salt solution—
Prepare as directed in the
Assay under
Docusate Sodium.
Procedure—
Dissolve about 100 mg of Docusate Potassium, accurately weighed, in 50 mL of chloroform in a glass-stoppered, 250-mL conical flask. Proceed as directed in the
Assay under
Docusate Sodium, beginning with “Add 50 mL of
Salt solution.” Each mL of
Tetra-n-butylammonium iodide solution is equivalent to 3.118 mg of C
20H
37KO
7S.
;)
for 4 hours: it loses not more than 3.0% of its weight.